1. Field of the Invention
The present invention relates to a film winding/rewinding apparatus for winding a film after cocking a diaphragm, a mirror, and a shutter of a camera and rewinding the film at a predetermined time.
2. Description of the Related Art
Heretofore, various film winding/rewinding apparatuses have been proposed. In these apparatuses, if a film winding operation is not completed in a predetermined period of time, it is decided that the last frame of the film has been wound.
However, according to the above-described deciding method, it is not decided until a predetermined period of time elapses after tension is applied to the film that the last frame of the film has been wound. Therefore, it takes long to detect that the last frame has been wound.
Similarly to the film winding apparatuses, various constructions of film winding apparatuses have been proposed. One of them is that a spool is driven by a motor and a film winding-stop member is rotated in association with a sprocket.
In the above-described construction, however, when the film travels in the film winding direction, the sprocket is rotated by the film. As a result, the sprocket rotates at a speed lower than that of the spool. Therefore, immediately after the film winding-stop member is stopped in association with the feeding of one frame of the film, tension is applied to the film, with the result that the perforations of the film may be broken. Even though the perforations are not broken, a shock is imparted to parts provided adjacent to the back lid of the camera, which makes a photographer feel uncomfortable. Therefore, there has been a demand for the development of a camera in which tension is not applied to the film.
Another example of a film winding apparatus has been proposed: A differential gear mechanism having a planetary gear mechanism is connected to a motor, and a film winding mechanism is connected to the planetary gear mechanism of the differential gear mechanism. A film winding-stop member for stopping the film winding mechanism from driving when one frame of the film is wound by the film winding mechanism is connected to the film winding mechanism. A cocking mechanism for cocking a diaphragm, a mirror, and a shutter is connected to the planetary gear mechanism through a rotation cam. A film winding-stop lever for stopping the rotation of the film winding-stop member is provided. In this film winding apparatus, after the operation for cocking the diaphragm, the mirror, and the shutter is completed due to the rotation of the rotation cam, the film winding-stop lever is disengaged from the film winding-stop member. When the planetary gear mechanism is driven by the motor, the planetary gear mechanism drives one of the film winding mechanism and the cocking mechanism which has the smaller driving load than the other.
According to this construction, the motor is driven after the completion of exposure, whereby the planetary gear mechanism is driven. At this time, the rotation of the film winding mechanism is stopped by the film winding-stop member which engages with the film winding-stop lever and the load on the cocking operation to be performed by the cocking mechanism is smaller than the load on the film winding operation. Therefore, the planetary gear mechanism rotates the cocking mechanism so that the diaphragm, the mirror, and the shutter are cocked by the cocking mechanism. After the cocking operation is completed, the film winding-stop lever is disengaged from the film winding-stop member by the rotation cam and a cam engaging member engages with the rotation cam. As a result, the rotation of the rotation cam is stopped and the planetary gear mechanism drives the film winding mechanism to wind a film winding operation. When one frame of the film has been wound, the film winding-stop lever engages with the film winding-stop member. As a result, the rotation of the film winding-stop member is stopped, which in turn stops the film winding mechanism from driving. Thereafter, the rotation cam is rotated again through the planetary gear mechanism and when the cam engaging member is disengaged from the rotation cam, the motor is stopped from driving, whereby the film winding operation is completed. When tension is applied to the film while the last frame of the film has been wound, the rotation cam is rotated through the planetary gear mechanism without the engagement of the film winding-stop lever and the film winding-stop member. When the cam engaging member disengages from the rotation cam, the motor is stopped. Thereafter, a film rewinding operation starts.
However, according to this construction, the film winding-stop lever engages with the film winding-stop member during the cocking operation. Therefore, the load on the film winding mechanism is greater than the load on the cocking mechanism and the cocking operation is reliably performed. But if the load on the film winding mechanism is small in disengaging the film winding-stop lever from the film winding-stop member by the rotation cam after the cocking operation is completed, the film winding mechanism is rotated by the planetary gear mechanism before the film winding-stop lever completely disengages from the film winding-stop member, with the result that the film winding-stop lever remains in contact with the film winding-stop releasing portion of the rotation cam. Accordingly, even when the feeding of one frame of the film is completed, the film winding-stop lever does not engage with the film winding-stop member. In this case, it may occur that more than one frame is fed forward.
Further, according to this construction, it is desirable to prepare the subsequent film winding operation in disengaging the rotation cam and the cam engaging member from each other under a small load after the film winding-stop lever engages with the film winding-stop member as a result of the completion of the feeding of one frame of the film. However, if the load on the disengaging operation is too small, the cam engaging member disengages from the rotation cam before the film winding-stop lever engages with the film winding-stop member when the load to feed the film becomes larger than that of normal operation. As a result, it may be erroneously regarded that tension has been applied to the film. Accordingly, the load is required to be heavy to some extent in disengaging the cam engaging member and the rotation cam from each other in order to securely detect that tension has been applied to the film. As a result, the load required for the disengaging operation in preparation for the subsequent operation becomes great. In this case, when, for example, the voltage of a battery is lowered, the rotation cam and the cam engaging member cannot be disengaged from each other.
Further, various constructions of film rewinding apparatuses are known. For example, a film is always pressed against a spool by a film pressing roller. Therefore, when the film is wound, the film is pressed onto the circumferential face of the spool by the roller so that the film is reliably wound around the spool. And a film rewinding fork and the spool are rotated by a motor so as to rewind the film into a patrone connected to the film rewinding fork.
According to this construction, although the film which has been wound around the spool is loosened in the spool chamber by the rotation of the spool in the film rewinding direction during the film rewinding operation, the film is kept pressed against the circumferential face of the spool by the roller while the film is being rewound. Therefore, due to the difference between the film rewinding speed and the rotational speed of the spool, the film is rubbed with each other and damaged or a heavy load is applied to the film rewinding mechanism due to the load of the spool.